Electronic and nuclear fluxes induced by quantum interference in the adiabatic and nonadiabatic dynamics in the Born-Huang representation.

We perform an electronic and nuclear flux analysis for nonadiabatic dynamics and its corresponding adiabatic counterpart, both of the wavefunctions of which are represented in the Born-Huang expansion. It is well known that the electronic-nuclear configurations (terms) in the expansion of the total wavefunction interfere each other through the nonadiabatic interactions and give birth to electronic and nuclear fluxes. Interestingly, even in the adiabatic dynamics without such nonadiabatic interactions, a wavefunction composed of more than one adiabatic state can undergo interference among the components and give the electronic and nuclear fluxes. That is, the individual pieces of the wavepacket components associated with the electronic wavefunctions in the adiabatic representation can propagate in time independently with no nonadiabatic interaction, and yet they can interfere among themselves to generate the specific types of electronic and nuclear fluxes. We refer to the dynamics of this class of total wavefunction as multiple-configuration adiabatic Born-Huang dynamics. A systematic way to distinguish the electronic and nuclear fluxes arising from nonadiabatic and the corresponding adiabatic dynamics is discussed, which leads to the deeper insight about the nonadiabatic dynamics and quantum interference in molecular processes. The so-called adiabatic flux will also be discussed.